The present invention refers to a torque converter transmission having a rotating casing, which is connected to a driving source, and in which the pump part, the turbine part, and the reactor part of the torque converter are mounted.
Torque converters of this kind are previously known, in which the pump part is constantly connected to the rotating casing and the turbine is connected to the output shaft. The said prior art converters are under certain conditions subject to some disadvantages, and in most applications the torque converters are necessarily combined with additional structures, which however do not solve all of the serious disadvantages. The Jandesek U.S. Pat. No. 2,607,456 shows an arrangement in which the pump part is releaseable from the rotating casing. This invention therefore has an object to propose a new and improved torque converter transmission of the type in which the pump part is releaseable from the casing.
A torque converter of the present type may be combined with step gears of power shift types or synchromesh types or it might be connected directly to the driving wheels by gears and shafts.
Such a torque converter transmission may also have a lock-up clutch, but in all applications there must be the possibility to release the torque transmission through the torque converter and/or torque absorption by the torque converter in one way or another. This may be done in the power shift gear by releasing the clutches or brakes, or a release clutch for braking the drive line may be provided in front of or at the rear of the torque converter, or a dog clutch having means for connection may be provided. In the case where the release clutch is provided on the primary side, i.e. in front of the torque converter, certain difficulties will arise, in particular in a torque converter of the rotating casing type, since a relatively large mass is connected directly or indirectly to the primary side of the gear train following the torque converter, and since the speed of the main part of said large mass changes for each connection to drive or for each change of the drive connection, but also because there are difficulties in providing power take offs, and further because the indirectly connected mass, at the change of connection, will synchronize slowly and during the synchronizing generate torque, which will prevent the change of drive before the torque disappears.
If on the other hand the release clutch is provided on the secondary side of the torque converter the clutch must connect under a torque, which may be three to ten times stronger than the engine torque, which requires a strong force to close the clutch or even a large size friction clutch. Further, when closing said clutch the torque limit for the coupling will also generate corresponding stresses to the connected drive line. At each connection a large torque wave will also be transmitted to the vehicle. Frequent connections also require either large friction surfaces or special arrangements for cooling the friction surfaces of the torque converter.
Irrespective of whether the coupling is mounted in front of or at the rear end of the torque converter it is impossible to obtain soft connections or soft shifts of the connected gears. Further, if the coupling is provided in front of the transmission there will be difficulties in providing for power take offs, and this arrangement will also extend the period between connection and drive and will form an inconvenient effect on the engine by reducing its speed to synchronize the mass of the engine and the mass of the torque converter primary part, and it will also eliminate the advantage of a rotating casing torque converter as a dampening means and a part of the engine fly-wheel mass.
It is therefore clear from the above that is is impossible to obtain ideal connections or disconnections of the torque converter irrespective of whether the release clutch is provided in front of the torque converter or at the rear end thereof.